1. Field of the Invention
This invention relates to prostheses for replacing natural intervertebral discs and more particularly to endplates incorporated into such prostheses for contacting the bodies of vertebrae adjacent to such prostheses.
2. Background Art
Prostheses for replacing a damaged or degenerated intervertebral disc often incorporate a relatively hard endplate intended to contact the body of an adjacent vertebra, fix the prosthesis in its intended location, and transfer spinal loads to other elements of the prosthesis.
A great variety of designs for such vertebra-contacting endplates have been proposed, and many have been experimentally implanted in patients, and thereby tested for safety and efficacy. However, the mechanical and physiological requirements for satisfactory performance of such endplates are complex and not easily met. Furthermore, the surgical procedures for implantation of intervertebral prostheses are complex and place great demands on the skill of the surgeon, which in turn establishes a need for prostheses adapted for uncomplicated implantation. Consequently, development of satisfactory designs for such prostheses, and, in particular, for the vertebra-contacting endplates thereof, has required much effort over along period of time. Furthermore, because of the great variation among individual patients and the many and various possible disorders afflicting the natural intervertebral disc, it is desirable for the surgeon to have a variety of designs available for selection to treat a particular patient.
Accordingly, a need has continued to exist for intervertebral prostheses having endplates that are well adapted for ease of implantation and for effective performance after implantation to relieve the distress of disorders of the natural intervertebral disc.